Forge (also called node-forge) is a native implementation of Transport Layer Security in JavaScript. Prior to 1.4.1, node-forge parsed deprecated extension OIDs 2.5.29.10 and 2.5.29.13 as basicConstraints, and pki.verifyCertificateChain() used the first extension with that name. Exploitation requires a CA trusted by the application to issue a certificate carrying an attacker-supplied deprecated-OID extension, commonly because the CA copies extensions from a certificate signing request. By placing a permissive deprecated extension before the genuine 2.5.29.19 basicConstraints extension, the certificate holder could have the certificate accepted as a CA and issue certificates for arbitrary names, enabling server or client impersonation. If the issuing CA adds a keyUsage extension without keyCertSign, node-forge rejects the chain. This issue is fixed in version 1.4.1.

Affected: npm: node-forge

### Summary node-forge parses certificate extensions with the deprecated OIDs `2.5.29.10` and `2.5.29.13` as `basicConstraints`, and `forge.pki.verifyCertificateChain()` used the first extension with that name. A certificate with a forged deprecated-OID extension (`cA` TRUE) before its genuine `basicConstraints` extension (`cA` FALSE) is accepted as a CA certificate, and the same technique can hide a `pathLenConstraint`. Fixed in node-forge 1.4.1.

### Details `lib/oids.js` maps the deprecated certificate extension OIDs `2.5.29.10` and `2.5.29.13` to the name `basicConstraints`, the same name as the RFC 5280 extension `2.5.29.19`. `certificateExtensionFromAsn1()` in `lib/x509.js` decodes extensions by name, so these extensions are decoded into the same `cA` and `pathLenConstraint` fields. `cert.getExtension()` returns the first extension with a matching name, and `pki.verifyCertificateChain()` looked up `basicConstraints` by name.

As a result, a certificate that contains a `2.5.29.10` (or `2.5.29.13`) extension with `cA` TRUE before its genuine `basicConstraints` extension with `cA` FALSE is accepted as a CA certificate. The same technique can hide a CA certificate's `pathLenConstraint`. A deprecated-OID extension on its own also satisfies the check added for GHSA-2328-f5f3-gj25 (CVE-2026-33896) that `basicConstraints` is present. RFC 5280 section 4.2.1.9 defines basicConstraints only as `id-ce 19` (`2.5.29.19`), and the path validation checks in section 6.1.4 apply to that…

Affected: Ubuntu:20.04:LTS: node-node-forge, Ubuntu:22.04:LTS: node-node-forge

Forge (also called node-forge) is a native implementation of Transport Layer Security in JavaScript. Prior to 1.4.1, node-forge parsed deprecated extension OIDs 2.5.29.10 and 2.5.29.13 as basicConstraints, and pki.verifyCertificateChain() used the first extension with that name. Exploitation requires a CA trusted by the application to issue a certificate carrying an attacker-supplied deprecated-OID extension, commonly because the CA copies extensions from a certificate signing request. By placing a permissive deprecated extension before the genuine 2.5.29.19 basicConstraints extension, the certificate holder could have the certificate accepted as a CA and issue certificates for arbitrary names, enabling server or client impersonation. If the issuing CA adds a keyUsage extension without keyCertSign, node-forge rejects the chain. This issue is fixed in version 1.4.1.